1. Field of the Invention
The present general inventive concept relates to a disturbance compensation method and apparatus, and more particularly, to a method and apparatus to safely repress disturbances from being applied to a system from the surroundings in which the system is used.
2. Description of the Related Art
The present general inventive concept is related to inventions disclosed in Korean Patent Publication No. 2001-017826 and Japanese Patent Publication No. 1993-242509, which are hereby incorporated by reference.
Korean Patent Publication No. 2001-017826 relates to technology that measures the amount of disk unbalance by analyzing a vibration frequency of a hard disk drive, and Japanese Patent Publication No. 1993-242509 relates to technology that improves anti-disturbance characteristics of an optical disk drive.
A conventional hard disk drive is a data storage system that contributes to the operation of a computer system by reading data written on a disk through a magnetic head or writing data on the disk through the magnetic head. As hard disk drives increase in terms of capacity, density, and compactness, the density in a rotating direction of the disk of the hard disk drive (bits per inch (BPI)) and the density in a radial direction of the disk of the hard disk drive (tracks per inch (TPI)) have increased, and thus hard disk drives require finer operating controlling mechanisms.
The purpose of the controlling mechanisms is to follow the track of a hard disk drive by keeping the magnetic head in the center of a target track of the hard disk drive. However, many disturbances to the hard disk drive can cause a tracking error. Particularly, a microdrive of a portable device is especially susceptible to such disturbances such as a vibration.
Thus, when a hard disk drive experiences disturbances, the effects of the disturbances cause a position error signal to immediately appear, and reduce the read/write performance of the hard disk drive. Accordingly, the conventional hard disk drive is designed with a built-in controller to detect a characteristic of an applied disturbance and to compensate for the applied disturbance in order to reliably maintain the read/write performance when the hard disk drive is subjected to the disturbances.
However, external vibrations being applied to a hard disk drive often have different frequency ranges and phases depending on the conditions and circumstances. Even when a controller with a high gain is used to remove the effects of these external vibrations, the use of the controller compromises the stability of the entire system.
A conventional “Q filter” disturbance observer, which is used to remove the effects of the disturbances, has fixed frequency characteristics for stable system operation, but the “Q filter” disturbance observer is unable to effectively remove the effects of the disturbances applied to the system from the surroundings in which the system is used.